The present invention relates to a fuel supply system equipped with a transfer pump which is driven with a traveling energy of fuel diverged from fuel to be supplied to an internal combustion engine from a fuel pump.
As disclosed in Japanese Patent Provisional Publication No. 2000-257526, various attempts have heretofore been made to provide a saddle fuel tank that straddles a propeller shaft or a fuel tank that incorporates therein a turning reservoir to preclude fuel from being forced to one side due to a centrifugal force created during cornering.
The saddle fuel tank has an inner structure formed in two independent fuel sump portions separate from one another that border the propeller shaft, and is arranged such that fuel is transferred from one fuel sump portion to the other fuel sump portion in which a fuel pump is disposed. Further, with the fuel tank in which the turning reservoir is disposed, an attempt is made to transfer fuel from an exterior of the fuel tank to an interior thereof.
To achieve such fuel transfer, a jet pump is used which draws fuel through the use of a traveling energy (flow speed) of fuel returning to the tank to enable fuel to be transferred without the need for using an extra drive unit such as a motor.
A discharge rate of the fuel pump for fuel to be supplied to the internal combustion engine is designed to vary depending on a demanded fuel flow rate of the internal combustion engine, with the discharged fuel stream partly forming an excess stream of fuel flowing through a pressure regulator or a stream of fuel bypassing from fuel at a feed side and serving as a return fuel stream to be fed back to the fuel tank such that these streams create a drive source for the jet pump previously mentioned.
However, with such a fuel supply system of the related art, since the jet pump is driven with a stream of a portion of fuel discharged from the fuel pump, a compensation flow rate (flow rate size) of the fuel pump is determined with a sum of the flow rate of fuel consumed with the internal combustion engine and a driving flow rate of the jet pump.
For this reason, in a case where the driving flow rate of the jet pump is formed with feed side fuel, the discharge rate of the fuel pump should include an additional driving flow rate of the jet pump and, hence, the flow rate size of the fuel pump must be increased to an excessively higher level than required.
Further, in a case where an approach is made to use a fuel pump of a variable volume type, since as the demanded fuel flow rate of the internal combustion engine increases, the fuel pressure is raised to cause the injector to atomize fuel in a fine mist or to allow a dynamic range to be increased, a leakage of fuel increases at the high fuel pressure side due to a feed-back of fuel pressure, i.e. the flow rate of return fuel increases, resulting in a need for a further increase in the flow rate size of the fuel pump.
Accordingly, the presence of such an increase in the flow rate size of the fuel pump induces an increase in the electric current necessary for driving the fuel pump with a resultant deterioration in fuel consumption, additionally causing disadvantageous results such as noises or vibrations due to an increased drive force.
It is therefore an object of the present invention to provide a fuel supply system with a transfer pump which enables a fuel pump to have a lowered flow rate size by providing a capability of reducing the flow rate of fuel to be diverged to the transfer pump in accordance with an increase in a demanded fuel flow rate of an internal combustion engine.
According to an aspect of the present invention, there is provided a fuel supply system with a transfer pump, comprising: a fuel pump supplying fuel to an internal combustion engine; a fuel tank having a first fuel sump portion in which the fuel pump is disposed and a second fuel sump portion formed separate from the first fuel sump portion; a transfer pump driven with a traveling energy of divergent fuel diverged from a portion of fuel to be supplied to the internal combustion engine from the fuel pump to transfer fuel from the second sump portion to the first fuel sump portion; and a divergent fuel control unit disposed in a supply line of the divergent fuel to decrease the flow rate of the divergent fuel in dependence on a demanded fuel flow rate of the internal combustion engine.
According to another aspect of the present invention, there is provided a fuel supply system with a transfer pump, comprising: means for supplying fuel to an internal combustion engine; a fuel tank having first fuel sump means in which the fuel supplying means is disposed and second fuel sump means formed separate from the first fuel sump means; fuel transfer means driven with a traveling energy of divergent fuel diverged from a portion of fuel to be supplied to the internal combustion engine from the fuel pump to transfer fuel from the second sump portion to the first fuel sump portion; and divergent fuel control means disposed in a supply line of the divergent fuel to decrease the flow rate of the divergent fuel in dependence on a demanded fuel flow rate of the internal combustion engine.
According to the other aspect of the present invention, there is provided a method for supplying fuel to an internal combustion engine, the method comprising: preparing a fuel pump supplying fuel to an internal combustion engine through a primary fuel passage; preparing a fuel tank having a first fuel sump portion in which the fuel pump is disposed and a second fuel sump portion formed separate from the first fuel sump portion; locating a transfer pump, which is driven with a traveling energy of divergent fuel diverged from a portion of fuel to be supplied to the internal combustion engine from the fuel pump, in a divergent fuel passage connected to the primary fuel passage; allowing the portion of fuel, passing through the primary fuel passage, to flow into the divergent fuel passage to drive the transfer pump for transferring fuel from the second sump portion to the first fuel sump portion; and controlling the degree of fluid communication between the primary passage and the divergent fuel passage to vary the flow rate of divergent fuel in dependence on a demanded fuel flow rate of the internal combustion engine.